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For some data centers, a standard virtual switch approach is enough for administrators. But for those who want more capabilities and the ability to create and configure switches at the vCenter server level, admins need to learn how to manage a vSphere Distributed Switch.
To be fair, the vSphere Standard Switch offers more than its name implies. However, centralized management is a an enticing feature for a lot of data center admins and when it comes to switches, the VMware vSphere Distributed Switch (vDS) can monitor the network configuration of each ESXi host that is associated with the switch. Steven Pantol and Christopher Wahl take a deep look at the vDS in Chapter 9 of their book, Networking for VMware Administrators. The authors explore how the vDS expands on the Standard Switch's support of Cisco Discovery Protocol with support for the link layer discovery protocol. The chapter also covers NetFlow, port mirroring and load balancing -- three of the more popular features associated with the vSphere Distributed Switch.
Since a vSphere Distributed Switch is managed through vCenter, some admins might be hesitant. What happens if and when vCenter goes down? Does that mean the vDS will stop working? Pantol and Wahl explain what to expect in this excerpt:
"The short answer is no, switching will continue without interruption. But, hey, we have a couple hundred pages to go, so let’s get into the long answer. While it’s true that the brains of a VDS lay with the vCenter server, there is a cached copy of the VDS configuration kept on every vSphere host and updated every five minutes. If vCenter fails, the host continues to use this cached copy of the VDS configuration. You can log into your vSphere host via Secure Shell (SSH) and see the file if you browse to /etc/vmware/ dvsdata.db. The cached database is shown in Figure 9.2.
When the vCenter server comes back online, you might see a few errors appear stating that the VDS configuration is not synchronized to some of your hosts. This will clear up shortly as the vCenter VDS configuration is pushed down to the vSphere host during the regular five-minute update interval."
Challenge your vSphere Distributed Switch knowledge with this quiz